# Boot loader Source: [https://docs.qualcomm.com/doc/80-70014-4/topic/bootloader.html](https://docs.qualcomm.com/doc/80-70014-4/topic/bootloader.html) The boot loader software runs when the system is powered on. It serves as an interface for loading the operating system and other required applications. Qualcomm chipsets, including the ones supported by Qualcomm Linux, use a multistage boot process with the following stages. ![](data:image/png;base64,UklGRoIdAABXRUJQVlA4THUdAAAvyMM9AH/lppEkScrhT2NJHY6z9uswZkFAaCTJkZTLH9YxOCj27VQ4aBtJklxUlj/A724y/3d4oBBEEJUVXayL9xBqSBCVLmpWmRFqujBEqIhQgZrwAYgvygYUCBUmKIwFoPIe5mCZAQAVqLl/D6jYAIEgAAKQIAzFgADCAjN2iwRRA4kISkYJNQT+j59MgBnX9wFbJKACEDYg0QRRCYJAuH95/zPDcv3mPYS9OL+O7X7+cn4fxvmTOQGA5y+V43YR739+95tUILeNJEkS/Tc7s2ru3W9ETECf6a/fGy7phRIMl6XMUK6vSrd09MIrD280qmdgkDWa3rOzy6EOddf6hIdp6bj1Nf3LO2HYtk1tJFce6u2kd5bZ20nPLHWylBwOMzMzM0cHwswMQ52BhcGe+Exv/UixZKtmug+UXW/Z5XLX+0X0fwJ8O5JkSZJtW1+zPuL2uH6oXsfvu4Vn5K26x/QXBZQVMChgrBH9n4De/5/6nTvHBuox9t+cpxjFeYphnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnKcY4zzFGOcpxjhPMcZ5ijHOU4xxnmKM8xRjnJ/gP3eQtglCGQLcQTJvE4QyBLBDWCg7xSCUnWIQypDbd9vtdx5c7kpy0zjMuG0LaiBDa89dS4+9+/vHTj11/vKgI8+mT3uYdz+2dNeea2srW30evK4jLW66m7y5KqiBDKe1/sdOXBx09LjY7R9qzvVbq/feuK8rLU0nbmu3cbveTabsSkvTidvabdLy3Xv/6UM/P37m7IW/D7pxuGBktvjwv+z1S1VAUYbPnn1vPTro+GO7b1bf7C7/+Pt+dOzUU+cvDzrybPq0R/jAC5b6exoyo3/8A+HYqfn08qAjz6a7HuEDbqm/pwn+0NqnNi4NurnZ+Owzh68vBzWQITPrv/HsQAPN6/uzWp61uOtjJ+Kgo8fFx7ceOFDbAeNlEdnR40K8QU1Ls/ccZ7efvW+PLwVFGSpXXr6gJi5we3WzfW87Ouj4Y/H7axl7OcqOPxa/v4YDd7z1HLu/ffuVg2WgKENk9bPUSOsqmt31hrPUQPOmrQOVHfBvMqz5e70HUu/Bawu9CAkZACOwpZq9CtbnCyXjkC+Ak00hz75p60BVt7/ib9TD8auulIEayLDYt/e7A62ch+UqbnvZgpq4ePntFV15+YK11+AA2MbF+aHIxctvr6b/lYE+fqNfBmogQ2LPxkAzN2YV9D890MjPrVbipmxgRekIw0pvHT8cfNL125DT1QpuwE+pkz/vHSwBRRkK/Z8NtNP3y+zb+52BVv4g2FI2/IANizABAMkXIYkAIAJLMiAuDfGWYDxgAKkBoW46YKsDcDSZywY2TwBIQ/iDvTeUWj5NvVxIGSjKEFj/AjU0hhKzjYFmbsxKzThoXuaLyuEaOixvLFMPCPOCa1yW42H5aumzAtLyRbgxK3Pvbwe6KZMyUJT2WWqpLXb3D6mdv1gt4ThoQ2QCk+Eh9DJs3YxBa7zDDWw1OA5bN+MmNGkHy8yckzxQi6As4qvwF6vF1r8y0M9FKANFadtDf6grItPnnQQaRfZ7arNIajrEV5tPixz+DDX0i+uFgmHTAiMM6YBSm2ULpX3n+DrAF5tlu2lttgLAFvCkwbkU6y/DL64Xegl1NJSCorTs+WwIfLuQVPW/ztDiuMi/UkttIcumuizfgP0ZBZyP7FsSAGId9WVoizz0ey3540OloCitWvlWAwzJBMhpOnAkA3xFwQ/2rXneoZ/W1EMgHZDUV6DJrIb8yGF9Pg3qk5r9Nf4wLTCdN4ZAIB0g1TXbZdDKWxKIF812eY/0CDlwPOBFKL/2fFpgTD0dl4OitOnwkYYwBXjAAaRBAhgGwJMMABBJCw+C1kN+JJAMAPylANQAbLkAjloAWz3ALBJQmw39aUemeeusWQBHC0tS7FCg3lT8NBwXGLO5HpmG1cnyOCxvrMcmTPaFlOW5M2TGvPReNdf8QhznrXxLU2ReDorSotUnGpJkATYnbQAgMiIzBXBI3cyrTEPSIx16WJ43sWyNC2OxDA2uF+B82mQ177/qooUV4CQpqGn5OaGazHuKn+db85y5NIhJyrIOL0dtiH5DQSkc5+LleMdJReZYC9KVDaRf+VvznPuOaEqcVwBFac/yZgOyQyqQOZ4JEGkhzAQcLSw1KIP6ADwdEEkwJls3qcFhmUDogMtNu0ndhIfUpi9+wc3lnP6RygDYlAOAQCYA8D0P0CoMcNQAUgsWwLxK4GNHTWAuA6QWQH+oAC4DMGpDrIBUkw3nTUemOdPYpG4dpzmrT2rKxFUBRWkN2JTA1MkCkRGG9AgpICuhNnNIXzmSAlBgSQa2UFrwHsuowVE30Cajh7BZbpv9FYjcrUlFDmlLkgEwzBuufVlqcu1Xy7MKrq/W/18Nrlub5ZsOy2OxLIfltrjmBfDNk9UcN9GVictZ3tSUS1IJFGWIPcDcyiIsWaTIZj5AwDUvKPdb8stdt1lR6AXSIpKMgCVJgSWTo3BpC8rgeH2RusnFIbXpDzAO6IESRoO2wPWNZOsmXQbHoDXYNq3JMUnfvrmcI5u6AskBdRUVK8roskgYixgE9YEI0AGRBGOydZPvCYQOOKQG7SY1CYd0+dXAii0yhaQBIHmsSygNjg1wbhw9xKJZ7hehukk3rSZzCHXI90BpwSWAI5Q222Q5JvM+Ip/aCk2Doowsj8wCDemNbE96pFMPy7pgc7JJluNh2RbL0OA6P0wgA+CBUueONpCfkfcO8fWK0HhL/5cOijKqaIAkQPIK5kOeJAMAr1oX1XmHARy1IYvUA8zFAMafwiMw0wFCwOcEx+UtLXiVutmLIb35okkH9EAJo0G/J9m6STdtwTFohe2mXf5r1ewXUH8hUJSh1EqoV795bQ6ZjhaWTIBIARCHa9wKrvlqeRYG13nxcjS4tjbX8EK/WKaHZdksj8NyWyzrmzRrC75XwecB82kbhVIPobwsk2U6pEX/ML1/ht6/FRSlGzTpXxBdyjEBHEkLQxogOkB4ywDSVw2MKwMYPzCqCYzqAKm632BdVBN6aG2IZmtdyr+L4g0bOJ8V2V/DpH6U5mdofi8oSgcowL8iDaxj+zN+pHhH8sdP95wPletkXC6G/g4DcBxSBW2AsgHKAUYP0dAGHLUh7g1QagEsEhhtgLo0O+EUcAFIPUQDagFs9UAcQk1AbTb0d4CijL6/x6sBBWrhgQgkgKUHAgk4CkAKPDdAabChTOBeMMBYAG0BWw02BBAWwL4AXDwAlwP8IkV8g8NSQYftcI0XzXU8LAMIHZZ3lnpYHg2u+wPXANiaF9rDMjUujAUQl+B6Ac63gKJsB1ieV4AsA6Dc/HHDcTPDNS4QBtcPLGt1uO4LRC7iwlhcQ5NrLQ7xseW+LF8I9fWGdLkZN2OzXTZbg7KIyzEJCzRojVutQZts3aQDeqBstssGhe2QLpt9OQ7hctNuUpPwkNr0xU+sCYqy7SBVaBvK4PiHbUAbeC24bD2kNn1vKxwLdDMalMFWk3G5aZvUZIrQYS+G/DLB+XoCpHrYghbAflGsPYRuWqGE0mY7QApqs4XSAjetJnNva3A8xKVhEVpw2UCbjB7CZrlt9veBonSFBJEWmY4MyFabvTrMv1Tb5YtZlENqMkoUmzikWrA62iz3vaPJrILlMTh3NtAm43VY5ot9Ky/lOhmXq/wWCnA0OGzVAqgP1M+THPsDQbnfkt8MitIRYJgHVyBuGfxLl2wm2YzDtj6Wnzb3gnK/I27FYn4k3bRugrmoySyE8vqRoBW2a2gNxmTrJh3QA/W2Q2jeG1KDdpOahEO6/GZQlE6QIKSEpEFggCdJULea6XRNFYweOG6WhqRHyBLEbjJADVAGx7kxpDffkozLO0Nq0Dapmz6EN4dUk1SD/SnxHYbl0QOozbJsoJprfmhY3lnqYVkaXFsbqDcUy1uHZVsAQWhwnW8HRekCFjEvFPPWIbtckdqgwfYVbCHCdJOCsCA1Wb4wuM676MPy3mHZFktNrr0oQh3WdVmfj4Ffz7kc1WCr9qXUiw2kH7Ih+lYDpdbFawKj+iYHQuKODVmkHshDqgGM3w+K0gEAl2cysudeQZdrRg12g5dWCyjmETuJydagVeBszgsDGN/ihvZcvGdDFqleVBNo14FqLfQzivwOd5O5/PoN2ouv2QgoyshzAFPZLEDdElyHC0o9AH9umWICP4L+MjfHrzn0tzrgX+FhOT8KFGX0mSJMeZI09L34myvwuiFdrGOxCKN7xf4iid8p4Pwd+OfS/ixQlI6QMDsnsP8xHGIxsO+hmAN0z83XKPpb/bU3BYoy6lCNpe/xd5cLgLNoVUAK8SrAt/7XAIoy0mjgyuSWzfpYBDvfJpK44xG2n0BRRppHrKa8ddidLtQDp6BvGEght00EijLKEgTW30yHE9Rga0O5eUl6ZDtG2O0hUJQRRmMaEGGXS8oG1SBvsFiCsE0EijLCEsTaDvNX14yf7xG3i0BRRtev/wtIfgFYbhuBUK5eNfVpCeI2EijKVatf/79vEMpOMQhlpxiEslMMQtkpBqHsFINQdopBKDvFIJSdYhDKTjEIZXtbs8xvdKBzf5HoFevQZLktzs8HoVwDS5BZomDn/l4ecJTGdNyaN0D+VOGV/X1y+3VvjC9zu/4d8B9877Uwkgw4WWin393heySac7/jYx1+2e8y/BNSFFwro7d6t1PdaTHAUQFeDdBqAqUdDaEBVG49QKPRarSdwbaAvCTs305RcO3sUHqArQmc3A4DXDZw1ATOiw1QLwAuCZQHSGDn1uJopwKkTiRpAfmiw8MAZQNlAamy4f8B4wYoNYHSAvKnYN8LbTRad66GUsZMbcqmNbbm1tz+h2Nxj9FidIdm6uZ3UxRcQ5Pj4Wim7tTF1kzdocW4U4dVhxq5itadmqlNWRxlHHRojTFaD+PQWozuuJW6Qzu0GN2hhNqhHWqkZupgMbrj27Hc3hstavE6W7UOpea2UTtv7K32B9S9VTlFqTfWo8k1fwVFwbW2bLWoO6UTFqV2Ll6X6r6lHkrNfaM47p0WZakuSvdW5dw5eljtrcqRflGqOy1KtfZW5Xy3UEk/cC7HAeoFc3FQ3WnHJW5Eq3Mv1GQ5g2q8Gl/mdv3zKQqadFjvO6fuWJ8V4Yy+Ef2TGWQmd4aX9a9FsDx31MHDMixgXugAsRqgdFDdecNsKexQTaAd1GQ5d+pSi2Q5Mi90gHBwmSznJyj2e1Tgm7XL309R0LDyo4e33f7hAkkmODeuuX2/7h3KGNdv8GbCWQyU+4UKvKXzpDnZmqTeaO++oV3fGCj3rfat38PmaF/yI8pZRC8OpeZ+w95qo3nhxc5VUSq/l6JAD2j3z5egEERHD3Wjw+L8/ezU3O8qzg3NXkSreUc5h1Jz3zl025vjobRe7fyUnR+LVjM81GLnD2KEDuXhFq1DLYbS2GZoU284HAt0h/aronU4Zuj+vRQF7WmgPcAfBwBJGSBkRSvAAmi1gFQH2C8KYL/YwKgH2JcAdFAHZUO5gVhJAvVLkA5+sMO/xc9pSg+jTX3MjRppphazyK3NC1qHMkObumNwLEKLo/GqaB3Om4rW4dzJrU1oph5O0Tqcn+GQuiH3rQIo1wNsNYHyDR6gQw3oeGEBlJqw49XL+i0UBe35gxbHQ3ko6UFaCB1CXrTu1OB4OBajOzyUMitGh7Po0EN5OJqpsbXjVqg7tCDFBEcztal/L5ZeD4C+wQ1sNYBxWUAOtSiAUhMoV5vUjRpbbWAyVxZA+YaCYwGUdwrIoTSBowVQfrMfdvHjt0BR0IJ1La6XUikpTzKYYtfYaox7q3IWL0u1bl2z1aIOqnWrtSg12BxkRj2UmvtHEwgAkpABzqEsgL0oTrEsDeAC8GLvhF1AqRs4OtEQBow6QGuxIVPt+Cn+Uf5aO1T6b0RR0IbyZcB+oQUARxtIRuT9AerSlzZZjgn5Qg1gFgKtBsvTcfHW6GFpcgIpEOqguvOH86S1KQe9MDqcF15ja2wdymjd+YLxELpTd2gxDluhHHQoi7ZIPZRG//fAANq/EEVBu7ShFwV/KFWowK329cBeBdt6pRvGGJdv83aKAfHXcKSYYqVaH8jUCdXsxeudKqMTFqV2Oqi5tSij1cFiVMai/ovwezZNUdA67VzsVIaUJxlMIeXc2HlD/8RiUM8d3dvcq2F1Lv2iOB+jMXooNfcPR1JQTA1g7jRqs9wOUG/AwzLuHRn1UMVRd9rh/3RQFLSsUWMvOjQihUiHJI/WoW4UrcMZSjMXh1Je7FBpD6NNGVuHKkZ54UY1tlhEa4Y29esE27o11CW9CbzH9accKvp/OigK2rIO3cBWgzYADgltACDMK4DyhgVQ2kC63sCJvTCBVg+AagClA8wrN+BZjJ7RBMrfZlDPncOoDneU84bivCVaHVwZTf0suT82X2u04y3FWeX+AgB7BZCfVJxfp+MvS1HQkn+EQ+dQyh3aZaQWLa1DvcGNGvmR4Vj0qyb84XZ+qZ2f9wWHVpPSYtSMv42/wyYpCq4CCXMoN3Biv2iWowGMFkD5Djew/YgDtK8O/U+D8bpTO1SL82+OouBqzO9c1I8T0GoBqRv4g5pbi/IA+xKAunNDrjZgx4a4JFAfym1HQ6iMyhSph73ocFkcm/J2AWzduSEvQP9CHRYD1IatNsBRE3a0FpDqAPuXUxRcM+n0p+GPRVuM7tCdyiihnR6OZmpsHcrNKL1wpzZbY2umHs47aI19w6KN7XLvlTEK9B1Gh+NmlFZa47cKTcbiOKgZmqmbthjd4aGU+dUUBddKCurH2WqHe6tyFrk9GWW22WpRf0I12x3q3vfUTg+qe79F7bxjk7jOG602wKxKtS6h7u2Een6rox1qjKXaYVEq7d6qnMVP3RRFwbBJkAeQXy259pvmBet/YN+2nlYPJstZTLh7T3EMlqdZbnde8lZcwmGZ74hL3DI5bxjXwVmoAYw7L+lOtX69Vg+Ag2q0yXJMyF9NUTC0ilEzvtpWi3lLx6tR3fGvUru+FBU1OaExLjtdf0Z499OgX3SsivPC6FWwrb+RA8e+174e2L+XomB4dagW5xu491cozt8SpK5Tv9lWO9x5y+iw2Ftzr4bPO9SnxWhddgy1klns1OhFrgb13JpQz19AbnVjUSrtzhs68WspCtqVAICQJhggkIwAQh7lywLysoHjofRQ5oZxgH7HAH0BQhuoD8WGYwOjFpDqAK020GoA9Rdz+NU4FmPROpxVszU5ehhtykgt+jPMUNmfkambcThmvDi0mpQOow4uD6Xckq3xF7BTBzRTN23ROpyhNPO3UhS0K8KRHqSBY0RkRKRDjkAvij+6Q3fooe5QOpTGvlWoQ1m00pqhHa5XGRqojR7GYjS3Q2lsBy2OubXj34oGRi2A0gPlYbRRPQCqAYwfOVA3TKB9sdwfEBjm0Cq50gC21wIIX27gxL4j0H8BAnE4mrBjtABKG0h/KUVByxxJJilP0gi9JxnybIDRvVU5clRvpRqjHl6wLI1WBztUmVvLUGOrjNphp2oZox4W18unDqEAIJDBkAyGRAAQ1QDKHeqgGxgPMAqEmh3QB/gl/ikOt89m/BXrUxS0jXQA4GhCKtAEkkmBa3BMlnOoi3e2yrpWWzVDGfVQOy/Rt8aX0VocdTD3RVmXAVs9wPlNBKRDLARHwTG3dlgczW2HHspDKa2NJschNfd/O4rRxr8CRUHrHJBQ6jLabJdvO95dHepbHV83tGpA/S7pIkLS7sU1WjmL66VTNcbcWhzt/G+HA+BfgaKgWcubVXhLMhTynmTIiV5ku3NVnEVd/ryKfotGq4MdF+Z9MmqHO1fRN7TzojFv21weOjSALxFJhvQAR+3wDyrQLzbLvhX/9fhVa1IUNGxtUkUwZEShiIQOOcOogxatw3GHFiOt8Wo4urmXW4dj0crWDD+hKQ9jMbrD4ejGRo1tbD2ct03Whg8ZgFCFGlAWJ7fXDX9W2/W/PMubmnJJalEUNO2BI1XQAHBICvB7AEKOBRCqBVDqBkYPMK8cIHzBNVUHaFUg1ILzHhsYtYBQBwh1A1sFOLrzPUdMzmJziJDBUlI+JSTtvmiMZvOfhe696PjJNpdzZFNXIDlrU02ZrNahKGjcyrcr0UI7z7l7OiwCSJrXMiLyJFIgE5Sx9XB0QN2h0gvZepifabKWI5P2/OHWKR2YTxuY6N9hspZjjmhKvK8GRUHz8LCuoJd7TxwW9AA8yQCYkAoAnArwH7XYqgm0GrQCHH+mIybHxOHwH0qj/fxof80jJmfl25pi59UpCtqw/mc9sSEP3xoaXxHfS/2a357nzK2u2HkOHtYU9CpXFLQCL9aTKQo+b3QkhiP14V7+w80z0gMkywGA5/cACACQHkAkw4sMvJiGMGBWAEa7N3TnhhQ4dqjRetAE0MMmNIBv8XAvf/0vWvLX9coUBS155Ks68tVZkcO/HBVAHCl/DgWCbR4SRkgGhBRERjjSvIf0hhREBggp2ArlsDLaBUebtkA7LI7F/9a93amyL2psHerr/Xm9AF6iJQFVKwragtXf6MeuQ+F/GxWj9sUoOm2eJ+lflDpJkq6QQyTpLQOYUnNrUR8JtUON1oNGOxuNsVTzcnRCNfvrTVH00a9pyHhRlaKgPdizoRsbMxRf/4KOfP3hQg+7xr2HZGJSJA0AKRDhSAbDYMqcj+RHyk5z8hxKbSA9lDbL/eW+/nAh9P+kHaaPitVA0KaDe3+iF+MgJfCcn+vH79ZQXCYtMngtTw6Hg9i7Uxs0X6XfcrKGksunNWMhqFhR0Cpg7Us6AemVn23oxsYMZWdsmCfpbUpAMhZyiCS9bYF0eiJbGTVeDN9iY4ayB5/1c6341UQqUhS0Df1XntCFReijwhv3/lgvfh36pRh8sxAZEVMRJ0kU4mtBCmIbNq1BabRuXhipRX+tX+/tlwJWRSP+3aFiRUH7cFP/zWd1wOz256h27Ss68c1DqHKyaNRrAUSm6AFE40mD92TQA4hsw3B0h3qA3bwwgPFLLyaotP/qv2nC+HXPRcWKgmEA7F9619GuN7Z+Pyrvv+qELixe80yv2sVrTjQosNMu8Eyv4oNX3nFOA6zauqNXsVAwJIBbH7z3kycudrW4mE7sCuq8svqWszpg3u5cr2rn5kYHzs6dQ/VLs/cd73iz9+/xvaoVBcMDwMrhAy/8wI+OnXr6/OWuNJs+5RE++I8HDq/0at+/9O6jXW/8Xn8QdYqP4643jl5Q79wc+vzGpY5mNr58/0M3oXI1EAyXzOu33L037kNHXppO3NYtaOp0ffKJExe7Wlx8uv/8O1B3HHN3cbG+rhoXu/3xHWjgyqG9//zRnx8/c/bC3ztSuGBktvBu72SOGhUFw0hv9x8+8A8f+dGxU0+fv9yVZtOnPIJbPPvwSq+Z86lbfCQc87vnZ11pNn3KI7jFsw+v9Bp881b/7oPXoRsvbiIZUbMaCK66ZPYfmK7esYSO7K84Y9hrOs3URY+O7K84Y9jTexkIrtJsOxYKdoaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNw7f7zx2k32ocvv18B6nfaRyexN9pHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4/AMG4dn2Dg8w8bhGTYOz7BxeIaNwzNsHJ5h4vAQ4/AUE57i78QvDgA=) ## Primary boot loader (PBL) - Establishes a secure root-of-trust (RoT) and secure boot process for applications. For more information, see [Secure boot](https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-11/secure-boot.html). - Identifies the primary storage device and loads the secondary boot loader called the eXtensible boot loader (XBL). If any recoverable error occurs while loading the XBL image, the PBL enters the emergency download (EDL) mode. For more information on how EDL mode is detected, see [EDL device manager enumeration](https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-4/edl-device-manager-enumeration.html). - Loads XBL segments into the boot SoC internal memory. For more information on how PBL loads the XBL segments, see [Cold boot architecture](https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-4/bootloader-architecture.html). ## eXtensible Boot Loader (XBL) - Initializes the hardware, firmware images, CPU cache, MMU, boot device, PMIC, and DDR. - Sets up the RAM dump to SD card, USB driver, USB charging, thermal check, power management integrated circuit ([PMIC](https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-4/pmic-developer-touchpoints.html)), and low-power double data rate (LPDDR) clock functions. - Collects the RAM dump in two ways: - RAM dump over USB to the host PC - RAM dump to internal storage - Loads and verifies the Qualcomm^®^ Trusted Execution Environment (Qualcomm TEE), Qualcomm Hypervisor, and UEFI image. - Provides the XBL configuration (XBL\_CFG), which is part of the cold boot flow and includes PMIC and other driver settings. - Provides XBL with a Qualcomm-signed ELF segment to initialize the external protection units (xPU). - XBL\_CFG is a standalone binary with platform-specific configurations and settings. The XBL uses the XBL\_CFG driver to load and configure the required settings. The driver uses the binary to provide on-demand read access to each setting of XBL\_CFG. ## Unified Extensible Firmware Interface (UEFI) Video: Unified Extensible Firmware Interface (UEFI) Video: Unified Extensible Firmware Interface (UEFI) UEFI is the software interface between an operating system and platform firmware. It includes data tables with platform information, along with the boot and runtime service calls that the OS and its loader can use. Together, they create a standard environment for booting an operating system and running UEFI applications. Note: While runtime services are part of the UEFI specification, they are not enabled in the Qualcomm Linux boot flow. Qualcomm uses TianocoreEDK2, an open-source implementation available at [http://www.tianocore.org/edk2/](https://github.com/tianocore/tianocore.github.io/wiki/EDK-II/) which follows the [UEFI specification](https://uefi.org/specs/UEFI/2.10/). There are two build options – retail and debug. - The retail build has minimal debug features and an optimal memory footprint, making it ideal for production environments. - The debug build is ideal for development environments, with all debug features enabled. For developing a UEFI application, see [Unified Extensible Firmware Interface (UEFI)](https://docs.qualcomm.com/doc/80-70014-4/topic/uefi-develop.html). ## systemd-boot OS manager systemd-boot is a UEFI boot manager which executes configured EFI images. It supports systems with UEFI firmware exclusively and does the following: - Loads boot entry information from the EFI system partition (ESP), typically mounted at /efi, /boot, or /boot/efi during the Linux OS runtime and from the extended boot loader partition (XBOOTLDR) (mounted to /boot). The configuration file fragments, kernels, initial RAM disk (initrd), and other EFI images must be located within the ESP or XBOOTLDR. - Reads simple and generic boot loader configuration files, and selects one file per boot loader entry. All the files are in the ESP partition. To ensure that the Qualcomm Linux kernel can be directly run as an EFI image, you can use the `CONFIG_EFI_STUB` compilation option. For more information on EFI, see the following: - For EFI boot stub, see [https://docs.kernel.org/admin-guide/efi-stub.html](https://docs.kernel.org/admin-guide/efi-stub.html). - For a sample structure of the EFI partition, see [Systemd-boot in Qualcomm Linux Yocto Guide](https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-27/platform_software_features.html). **Parent Topic:** [Architecture](https://docs.qualcomm.com/doc/80-70014-4/topic/architecture.html) Last Published: Feb 02, 2026 [Previous Topic Architecture](https://docs.qualcomm.com/bundle/publicresource/80-70014-4/topics/architecture.md) [Next Topic Cold boot architecture](https://docs.qualcomm.com/bundle/publicresource/80-70014-4/topics/bootloader-architecture.md)